Surface charge printing for programmed droplet transport

The directed, long-range and self-propelled transport of droplets on solid surfaces is crucial for many applications from water harvesting to bio-analysis1–9. Typically, preferential transport is achieved by topographic or chemical modulation of surface wetting gradients that break the asymmetric contact line and overcome the resistance force to move droplets along a particular direction10–16. Nonetheless, despite extensive progress, directional droplet transport is limited to low transport velocity or short transport distance. Here we report the high-velocity and ultralong transport of droplets elicited by surface charge density gradients printed on diverse substrates. We leverage the facile water droplet…